Junfeng Li

Biomass based hydrogel as an adsorbent for the fast removal of heavy metal ions from aqueous solutions

In order to achieve the reutilization of waste biomass soybean dregs, a low-cost hydrogel, soybean dregs–poly(acrylic acid) (SESD–PAA) was prepared through a one-step reaction. The synthesized polymer was verified by Fourier transform infrared spectroscopy, thermogravimetric analysis, and scanning electron microscopy. As an adsorbent, SESD–PAA was used to remove Zn(II), Fe(III), Cu(II), and Cr(III) from aqueous solutions. The effect of pH, initial concentration, and contact time on metal ion adsorption was examined. It was found that SESD–PAA showed high and fast adsorption capacities for Zn(II), Fe(III), Cu(II), and Cr(III), which were 121.2, 78.5, 75.4, and 41.7 mg g−1, respectively. Moreover, before and after the adsorption of these ions, the hydrogels were analyzed by X-ray photoelectron spectroscopy, which confirmed that the metal ions were adsorbed by the polymer by interactions of carboxyl, hydroxyl, and amine groups with metal ions. Additionally, the adsorption process followed a pseudo-second-order kinetics model, the Fickian diffusion model, and the Freundlich adsorption model. Furthermore, the competitive adsorption of metal ions in mixtures and the desorption/regeneration capacity of SESD–PAA were investigated. As an efficient, low-cost, easily obtained, and environmentally friendly adsorbent, SESD–PAA was expected to be used for the processing of large amounts of sewage.

Electrospun hollow ZnO/NiO heterostructures with enhanced photocatalytic activity

ZnO/NiO hollow nanofibers with high photocatalytic activity are successfully fabricated by impregnating electrospun polyethersulfone (PES) nanofiber webs in nickel acetate and zinc acetate solutions and subsequent thermal treatment. From scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images, it can be observed that the morphology of the ZnO/NiO products is a hollow structure successively. According to statistics, the ZnO/NiO hollow nanofibers show diameters of approximate 414 nm with inner diameters of about 261 nm. Fourier transform infrared radiation (FTIR) and X-ray diffraction (XRD) measurements demonstrate that the product is composed of ZnO/NiO hollow nanofibers with hexangular structure ZnO and cubic structure NiO. The formation mechanism is studied in detail by TGA and DSC. The photocatalytic activity of the hollow ZnO/NiO heterojunction nanofibers for the degradation of methyl orange (MO) is much higher than that of pure ZnO and NiO nanofibers, which may be ascribed to the unique hollow structure and the highly efficient separation of photogenerated electron–hole pairs. Furthermore, the photocatalytic mechanism of the hollow ZnO/NiO nanofibers is expounded.

Electrospun carboxylic-functionalized poly(arylene ether ketone) ultrafine fibers optimization, characterization, and water absorption behavior

As a high-performance polymer, carboxylic-functionalized poly(arylene ether ketone)s (PCA-PAEK) was electrospun into ultrafine fibers and characterized. To optimize the process, a set of experiments were designed. As a result, the optimum condition was obtained and the polymer concentration was determined as the most important factor. Incidentally, the PCA-PAEK fibers were found to exhibit superabsorbent behavior. In order to investigate processing characteristics, PCA-PAEK fibers fabricated from different solution concentrations were employed and characterized. The results showed that porosity and changes in water contact angle and water absorbency decreased with an increase in concentration. In addition to a high water absorption capacity, the fibers exhibited good water retention and repeated water absorbency as well. The study on kinetics of water absorption and swelling behavior showed that the mechanism was dependent on the polymer concentration from which the fibers were electrospun. Moreover, both dry and wet PCA-PAEK fibers showed high mechanical properties. Due to these properties, the PCA-PAEK ultrafine fibers are potentially useful as a water-absorbent material.

Preparation of recycled graphite/expanded polystyrene by a facile solvent dissolution method

In this paper, the waste graphite/expanded polystyrene was used as a raw material to prepare recycled graphite/expanded (rGEPS) foam board. A convenient and facile way to regenerate graphite/polystyrene beads was proposed in this work. This can be applied in the further industrial production. The solvent could be recycled, which made the process more efficient and economic. The rGEPS beads were analyzed by TGA, FTIR and XRD. The results indicated that the properties were not deteriorated. Then, the test results of rGEPS foam board, such as water absorption, apparent density, bending strength, compressive strength, thermal conductivity and oxygen index, showed that the properties have reached enterprise standards of expanded polystyrene (EPS) foam board. The thermal conductivity was decreased by 13.16% compared with EPS foam board. Therefore, the prepared rGEPS foam board could be considered as a candidate of the thermal insulation materials in construction.